Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Thu
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Rain and prolonged warming are creating dangerous avalanche conditions. Watch for wet snow avalanche problems as you climb in elevation. Avoid traveling beneath large avalanche paths. Be cautious while traveling on and below corniced ridgelines. 

Problemas de aludes

  • Cornices

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Prolonged warming and rain may cause cornices to fail naturally. Be cautious and observant while walking on and near exposed ridgelines. Give the edge of ridgelines a wide berth and use vegetation or rocks as visual landmarks for safe travel. Avoid traveling directly below ridgelines with large cornices.

    (3/29/2024)

    Cornice were sporting new hats. These caps formed during from recent southwesterly wind. Cornices are more likely to fail during periods of prolonged warming. 

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Today’s rainline will hover around 6000 feet. Rain on snow is a recipe for avalanches. Expect to see rollerballs, pinwheels, and point releases out of steep terrain on all aspects. Keep a close eye on your slope angle. Wet avalanches can run through more densely timbered slopes that may not appear like obvious avalanche terrain. Expect this problem to diminish rapidly with the onset of cooler air.

    (4/1/2024)

    Debris from loose wet debris runs 2000 feet on steep slopes in the Flathead Range.

    Photo: Austin Seback/Sarah Williams

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    2–3

    Avalanche activity on a weak layer buried 2-4+ feet below the surface has diminished over the last couple of weeks. Although the likelihood of triggering a very large avalanche is low, the consequences are high. We are keeping this as a listed problem until cold air refreezes the surface. Until then, the safest bet is to give terrain where the problem exists a wide margin for error. That terrain is rocky, steep, upper-elevation slopes that face north.

    (4/1/2024)

    Very large hard slab avalanche that likely failed after the late February wind event. These avalanches appear to have characteristics of a persistant slab problem.

    Photo: Austin Seback/Sarah Williams

Avalanche Discussion

Today’s weather and avalanche forecast feels anything but simple. My dream of a cold front causing temperatures to come crashing down is not playing out. Unfortunately, the bulk of the precipitation will fall as rain. The rain/snow line is forecasted to hover around 6000 feet. Above that elevation, expect a couple of inches of fresh snow with moderate wind speeds. The weather today will lead to some dynamic avalanche conditions. I’ll break this down into two categories: below rainline and above rainline.

Below rainline:

The main question is: where will that be? Currently, remote weather stations are reading 40F up to 8000 feet! That elevation will drop throughout the day, but how fast is the question?

Wet snow avalanches will be likely below the rain/snow line. These should be mostly small, but expect to some larger avalanches on north-facing slopes where rain is falling on a dryer snowpack. The past few days of warm and sunny weather have thoroughly worked over south-facing aspects, so I would expect to see less avalanche activity there.

The wild card is what will happen once water makes it a buried facet/crust 2-4 feet below the surface. Predicting the timing of that is challenging. The snowpack on northern aspects has remained surprisingly dry through significant warm spells. Liquid precipitation, warm temperatures, and cloud cover may be rapidly changing the snowpack on north-facing slopes today.

Travel advice below the rainline is relatively simple, stick to lower-angled slopes free of overhead hazards.

Above rainline:

Winds at upper elevations are turning at speeds capable of transporting snow with little snow available to move around. Slabs of drifted snow will mostly involve freshly fallen snow. A very humble and key observation came in from the alpine yesterday (read it here). A rider triggered a Wind Slab that took them for a short and harmless ride. This is actionable information for us all to use today. If you venture into the alpine, look for and steer around slabs of drifted snow.

It's hard to believe it, but FAC's last daily forecast will be on Monday, April 8th 2024.  After that we will continue to issue conditions updates on Tuesdays and Fridays until May or as conditions dictate. 

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